Electric furnace



Aug. 14, 1928 G. M. LITTLE ELECTRIC FURNACE Filed Aug. 9, 1924 NW1 \g E 1 WITNESSES:

@wfa, 1% 6' ATTORNEY Patented Aug. 14, 1928.

GEORGE LITTLE, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T WESTINGHOUSE ELECTRIC 85 MANUFACTURING COMPANY, A. CORPORATION OF PENNSYLVANIA.

ELECTRIC FUBNACE.

application filed August 9, 1924. Serial No. 731,050.

My invention relates to electric furnaces and particularly I I The object of my 1nvent1on is to provide a relatively simple and compact resistor memher for an electric furnace that shall be substantially self-regulating in its operatipn.

In practicing my invention, provide a refractory casing within which 1s located a plurality of refractory electric-conducting electrodes, the ends of wh1ch are located n abutting relation to each other.

Suitable means is provided for pressing the electrodes toward each other and for conducting current thereto and therefrom. Means is also provided for directing a stream of air against the unction of the electrodes.

In the drawings, Figure 1 is a View, in vertical section, of an electric furnace embodying my invention, Fig. 2 is a view, in vertical section, of a modified form of furnace embodying my invention, v

Fig. 3 is a schematic view, in s1de elevation, of a further modification, and n Fig. 4 is a schematic view of a still further modification of a furnace embodying my invention.

Referring more particularly to Fig. 1 of the drawing, I have there illustrated an electrio furnace 11 as comprising a. furnace casing 12, having a lurality of walls of any suitable refractory mat-insulating material usually employed in, the art. The furnace Walls may e of any suitable or desired dimensions' and in fact, the furnace casing may be of any suitable or desired dimensions and shape.

A plurality of elongated electrodes 13 and 14 are located inabutting and ahned relation to each other within a furnacechamber 15 enclosed by the walls of the casmg 12. The lower electrode 14 may be of copper and may be fixedly mounted in a suitable electrode support 15 and be prov1ded with a contact terminal member 16 to which the end of one supply circuit conductor (not shown) may be connected.

The upper electrode 13 is movable longitudinally through one of the walls of the casing 12 and, as illustrated in Fig. 1 of the drawing, tact terminal member 17 is provided, through which the electrode 13 extends and through which'it may move to compensate for the burning away of the electrode itself. The

electric resistance furnaces.

a combined stufiing box and constuffing box 17 may be filled with amass 18 'of granular electric-conducting material,

such as carbon or graphite, to assist in conducting current from the stufing box member 17 to the electrode 13. The other'supply circuit conductor .(not shown) may be electrically connected in the usual manner to the member 17.

Means for pressing the upper electrode 13 against the lower electrode 14 may comprise a weight 19 mounted on the upper end of the electrode, although any suitable means for providing pressure is within the scope of my invention.

Means for supplying a stream of oxidizing fluid, such as air, against the'junction' of the two electrodes comprises a conduit 21 extending into the furnace chamber 15 through one of the walls of the furnace, the inner end thereof being located adjacent to the'junction of the electrodes and Qconnected to a suitable source of supply.

In Fig. 2 of the drawings, I have'illustrated a somewhat different form of furnace comprising a casing22, having two lower inclined wall portions 23 and 24.- The plu-. rality of refractory walls surround a furnace chamber 25, an opening 26 being;pro vlded in one of the walls to permitof placn'g material into and removing it from the furnace chamber.

A pluralityof elongated electrodes 27 and 28, of electric-conducting material, extend through the walls 23 and 24 respectively. and have operatively associated therewith contact terminals 29 and 31 to permit of connecting the electrodes to the ends of suitable supply circuit conductors (not shown). The

contact terminals 29 and 31 are secured to conducting collars 32 and 33 loosely mounted on the electrodes and having any suitable means to conduct current thereto. Plates 34 and 35 of a suitable electric-insulating material, are located between the collars 32 and 33 to prevent leakage of current from the collars to the furnace structure itself.

The two electrodes 27 and 28 are disposed angularly relatively to each other and may, be located in a vertical plane, the inner ends thereof being located in abutting relation,

Means for causing the two electrodes to re-' main in abutting relation and to press the same together during the operation of the furnace, comprise a weight 36 that is connected by a plurality of chains 37 and 38 to the outer ends of the electrodes 27 and 28. The chains 37 and 38 run on a plurality of pulleys so located that the weight 36 tends to move the electrodes inwardly toward each other.

Vhile I have illustrated and described a specific means for providing pressure between the ends of the electrodes, I do not wish to be restricted thereto, as this forms no articular part of my inventiorn cans for providing a stream of oxidizing fluid, such as air against the junction of the electrodes, comprises a conduit 39 that is located in a plane other than that in which the electrodes are located and directs a stream of air against the unction.

In Fig. 3, I have illustrated a schematic form of construction in which the electrodes 41 and 42 are both movable. The upper electrode 41 is provided with a contact terminal 43, while the lower electrode 42 is provided with a contact terminal 44, both electrodes being freely movable relatively to the terminals. The terminal members 43 and 44 are held in substantially fixed positions near the junction of the two electrodes, by supporting members 45 and 46 respectively A plurality of weight members 4 and 48 may be connected to the respective electrodes 41 and 42 by pairs of chains 49 and 51, the latter running over fixed pulleys 52. In this construction, both electrodes are moved toward each other by substantially equal amounts during the operation of the furnace.

While no furnace casin is illustrated in Fig. 3 of the drawing, it is understood that the electrodes are preferably located within a suitable refractory casing.

In Fig. 4 of the drawings, I have illustrated, schematically only, the use of more than two electric-conducting electrodes to permit of connecting the same to a polyphase source of supply of electric energy. Electrodes 53, 54 and 55 may be located in symmetricallyspaced positions relatively to each other in either a vertical or a horizontal plane and any suitable or desired means, such as hereinbefore described, particularly in connection with Figs. 2 and 3 of the draw ing, maybe employed to provide proper pressure therebetween and to provide a stream of air against the junction of the electrodes.

I have found, by actual experiment, that it is possible to connect the electrodes to a suitable source of electric energy of relatively low voltage and to obtain a relatively high degree of heat at the junction of the two electrodes, and it is desirable to so locate the contact terminals that they will be near to v the junction, to prevent heating any appreciable length of the electrodes away from the Y junction.

The junction becomes incandescent and the current very quickly reaches a predetermined value that remains substantially constant. I have found, for instance, that when using graphite rods of substantially l" in diameter as the electrodes, that an applied voltage of six volts causes a current of substantially 550 amperes to traversesuch a circuit.' When raising the voltage to seven volts, the circuit was traversed by substantially 700 ampercs, and when employing 9 volts, the current was substantially 950 amperes, these values being maintained indefinitely, as long as the other conditions of operation were maintained the same.

During the above mentioned operation, the junction of the electrodes wassubjected to a steady stream of oxidizing fluid, such as air, and it is my opinion that the use of such an air jet is mainly responsible for this condition of operation, as the oxidation, which accompanies the operation of a carbonaceous electrode at or above red heat, is restricted to substantially the junction of the two electrodes and is prevented from spreading over any appreciable length of the electrode or electrodes adjacent to the end or ends thereof that are in contact. VVhen no'strcam of air is employed, the electrodes become incandescent-over a relatively large part of their length immediately adjacent to the junction and oxidize or burn away over substantially this portion, causing the electrodes to become very thin after a certain length of time and accompanied by the possibility of brealring of the electrodes and an interruption of the circuit, which conditions are en- 100 tirely overcome in the hereinbefore described construction and method of operation.

The device embodying my invention provides a'resistor furnace that may be operated in the open, thus making it unnecessary 105 to enclose the same in an air-tight chamber or to prevent the access of air to the incandescent resistors as has been found necessary in earlier types of resistor furnaces embodying carbonaceous resistor members.

The resistor is very stable, much more so than are furnaces, while givin temperatures which are substantially as high as those found in an arc furnace.

I have found that the power factor is very 115 high and that the operation of the furnace is very quiet, its performance not being affected by the presence of metallic vapors which usually cause disturbances in an arc furnace.

I have found it particularly easy to replace the electrodes in such a furnace within a very shorttime, thus permitting of placing the furnace back into operation in case of total consumption of electrodes, which consum 125 tion is. of course, greater than would be t e case if not subjected to the effect of a jet or stream of oxidizing fluid.

Various modifications and changes may be made without departing from the spirit and 130 scope of the invention, I desire, therefore, that only such limitations shall be placed thereon, as are imposed by the prior art.

I claim as my invention:

1. In an electric furnace, in combination, a plurality of alined carbonaceous electrodes, means for pressing the abuttin ends of said electrodes together continuous y, and means for restricting the oxidation of said electrodes. when traversed by an electric current, to substantially their junction.

2. In an electric furnace, in combination, a plurality of alined carbonaceous electrodes having their abutting ends in operative enagement' with each other, means for press ing said electrodes into continuous close contact with each other, and means for directin a stream of air against the junction of said electrodes.

3. In an electric furnace, in combination, a plurality of refractory electric-conducting electrodes located in abutting relation relatively to each other, means for pressing said electrodes toward each other to maintain said abutting relation, and means comprising a directed stream of air for restricting the oxidation of said electrodes, when traversed by an electricvcurrent, to substantially their junction. v

4. In an electric furnace, in combination, a plurality of refractory electric-conducting electrodes having their abutting ends in operative engagement with each other, means for increasing .the oxidation of said electrodes .at the junction thereof when traversed by an electric current, and means for maintaining the engagement of said electrode ends during operation.

5. In an electric furnace, in combination, a plurality of refractory electric-conducting electrodes having their ends in abutting ops erative engagement with each other and traversed by an electric current, means for maintaining a substantially constant pressure between said abutting ends, and means, comprising a directed stream of air, for limiting the oxidation of said electrodesto sub-= stantially the junction thereof, whereby a substantially constant contact resistance is obtained.

In testimony whereof, I have hereunto subscribed my name this 1st day of August,

GEORGE M. LITTLE. 

